With the recent addition of villager trading I've decided that it makes a whole lot more sense to get some of them moved into an isolated set of cells or pens. Something that would both keep them safe from zombies and also make them really handy for when I want to do some trading to build up my stock of emeralds.

Not that I intend to use the emeralds as money so much as emerald block will make a good decorative addition to some builds.